I won't ask which is better, as that is highly subjective. I know that reflective umbrellas can spill more light in close quarters, and are more easily caught by a gust of wind, but are cheap and easy to set up.

What are the pros and cons of soft boxes, shoot through umbrellas, and reflective umbrellas for portrait photography?

Does the answer depend on whether you're using studio lights or speedlights?

Is there a quantitative difference in the quality of light (contrast or softness) produced by each?

2 Answers
2

For me the main difference is a softbox generally has better control of the direction of the light. The softbox will have a flat diffusion panel on the front and possibly a raised edge that stops light spilling off to the side. You can add a grid to it to control the spill even more. While an umbrella, has a curved surface that reflects or diffuses light in a more uncontrolled way. If you were in a small room using a shoot through umbrella you'd get light spreading all over the place as well as where you were actually pointing it. This isn't necessarily a bad thing.

The softness/quality of light are so subjective but softboxes can have multiple diffusion panels so you might get a more even light spread. Softness if going to depend on relative size of source and subject, and contrast is going to be determined by your light source to subject distance. A silver reflective umbrella will probably give you higher contrast/more specular highlights.

Umbrellas are simple to put up and down and can be purchased very cheaply. They just mount to your light/light-stand with their pole so they are universal. Soft boxes usually have a specific mount and can be a pain to assemble.

There are brolly boxes/easy up softboxes which open like an umbrella but are enclosed and have a flat front of a softbox.

In short:
Umbrellas: cheap, easy to use, versatile, less spill control, reflective umbrellas are difficult to get close to subjects because of the pole.
Soft boxes: generally more expensive, more spill control, better for larger sizes, more even light spread, need to get them with the correct mount to match your lights

Great answer. I would agree the softboxes have more control and have more even spread of light. Good point about the subject difference with reflective umbrella. Another point of difference of course is the shape of the catchlight. Also umbrellas can be easier to use with IR controlled off camera flashes (easier to achieve line of sight from camera to flash)
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MikeWJan 17 '12 at 5:19

Softboxes spread the light and makes shadows not so strong compared with the umbrellas. Umbrellas concentrates the light more to the one spot compared with the softbox, so then you getting deeper shadows, concentrated light and more contrast. Of course it will depend on the sizes of the tools.